1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly, to the bonding of the sliders in such suspensions to the suspension flexure tongues.
2. Related Art
The flexure tongue of a magnetic or magnetic-optical recording head suspensions has as one of its functions providing a surface for bonding attachment of the slider. This surface is generally flat to provide the maximum bonding surface area between the slider and the flexure tongue. In some designs, this surface also includes a dimple to provide a point of contact and a point of rotation between the flexure and the applied load supplied by the load beam. The adhesive bond between the slider and the flexure tongue is required to carry some of the loads applied to the slider by the external environment. These loads include shear, tension, compression, and bending.
Of these loads, three immediately test the adhesive bond. Shear (horizontal) load between the suspension and the slider is due to friction of the disk, acceleration of the slider across tracks during accessing (moving to a new radial location on the disk), and horizontal (in the plane of the disk) shock from movement of the disk drive. The tension load the slider applies to the adhesive bond joint between the slider and the flexure tongue is due to vertical shock, and liftoff, as is the bending load. Tension and shear loads are the most significant.
To achieve an adhesive bond between the slider and the flexure tongue, typically one or more small deposits of fluid, curable adhesive, "dots", are applied to the flexure tongue portion of the suspension before it is moved into contact with the slider in a bonding fixture which holds the assembly in the exact correct position until enough cure of the adhesive has taken place that the assembled slider/suspension combination can be removed from the fixture safely, that is, without relative movement from the correct position. The cure is then continued without fixturing until the cure is complete. The adhesives are chosen for their low outgassing, long pot life, adhesion strength, environmental and safety compatibility, and cost. It is common to have an adhesive that will spot cure under UV light exposure, and then final cure under thermal (oven cure) process.
It is known to use a small hole or holes in the flexure tongue as shown in U.S. Pat. No. 5,008,768 to Carlson, Zarouri and Coon to enhance bond strength by forming a rivet-head like structure so that the adhesive will seep through the hole and form a three dimensional bond instead of a two dimensional bond. Other small holes are used to allow UV light to pass through the load beam and flexure to initiate the cure in some types of UV curing adhesives.